The Heavy Plow

The light scratch-plow (ard) of the Mediterranean world was adequate for thin dry soils but defeated by the deep wet clay of northern European river plains — precisely the richest agricultural land on the continent. The heavy plow, emerging between the sixth and ninth centuries, combined a vertical coulter that cut the sod, a horizontal plowshare that undercut it, and a curved moldboard that turned the cut sod over. It could break the clay the ard could not touch. But it required enormous draft power — typically eight oxen — which no single peasant family owned. The plow therefore required cooperative agriculture, producing the open-field system in which families held strips of land within larger communal fields, plowed cooperatively and farmed individually.